You can add content sets only to production projects. Content sets you add to a production project are automatically copied to any linked projects.
On the Projects tab, go to Projects > Your Project > Content.
Click the Add Content Set button.
Enter the content set name (required), description (optional). If you have created additional content labels other than the default Catalog label, select a content label.
The content set is added:
You can now add content to the content set. See Adding File System Content to Content Sets or Adding Repository Content to Content Sets.